Abstract: The reduction of octane requirement in a spark-ignited, internal combustion engine is achieved by introducing, with the combustion intake charge, a fuel and/or lubricant composition containing an octane requirement reduction amount of a substituted urea compound represented by the formula: ##STR1## in which X is an oxygen or sulfur atom, R.sub.1 and R.sub.3 are hydrocarbyl radicals having from 1 to 3 carbon atoms, and R.sub.2 is selected from the group consisting of ##STR2## Particularly useful as ORR agents are: (a) 4-[N-(2,4-xylyl) carbamoyl] morpholine;(b) 1-[N-(2,4-xylyl) carbamoyl] piperidine; and(c) 1-(2-pyridyl)-3-(3,4-xylyl)-2-thiourea.

Abstract: The reduction of octane requirement in a spark ignition, internal combustion engine is achieved by introducing with the combustion intake charge a fuel and/or lubricant composition containing an octane requirement reduction amount of a compound represented by the formula: ##STR1## where R, R' and R" are hydrocarbyl groups having from 1 to 3 carbon atoms.